1. Field of the Invention
This invention relates to a light emitting device that a light emitting element is mounted at the bottom of a concave portion of a case.
2. Description of the Related Art
A light emitting device using a light emitting element such as LED (light emitting diode) is known that is composed of the semiconductor light emitting element, a pair of leads electrically connected to electrodes of the semiconductor light emitting element, a resin stem equipped with a concave portion for housing the semiconductor light emitting element and the leads therein. For example, JP-B-3492178 discloses a light emitting device that the leads are disposed at the bottom of the concave portion of the resin stem and a transparent sealing material of silicone resin is filled inside the concave portion.
However, the light emitting device disclosed in JP-B-3492178 has a problem that the whole sealing material may move away from the bottom when conducting the moisture absorption reflow test since the resin sealing material has a relatively large linear expansion coefficient. This phenomenon becomes more significant when a part of the bottom of the concave portion is formed of the metal lead and the other part is formed of the resin material composing the case since local stress is generated in the sealing material due to the difference in adherence to the sealing material between the meal and the resin. If the resin material moves away from the bottom, the connection between the light emitting element and the leads may be broken such that the light emitting element fails to operate properly.